This disclosure relates generally to high density plasma reactors, and more particularly to high density plasma reactors with multiple top coils.
Plasma reactors are commonly used in semiconductor processing. For example, in high density plasma chemical vapor deposition (HDPCVD) processing, a plasma of process gases is generated in the reactor to deposit a film of material on a silicon wafer. It is important in semiconductor processing that the thickness profile of the film formed on the wafer be as uniform as possible.
A plasma reactor includes a chamber that contains the plasma, gases and the wafer, which is supported on a platform such as an electrostatic chuck. The chamber is typically formed of a metal, such as aluminum. The inside of the chamber may be covered with an insulating layer. The top or ceiling of the chamber is formed from a dielectric material. The reactor includes a planar top coil that is positioned above the ceiling. The coil is coupled to a radio frequency (RF) generator. The coil transmits RF energy into the chamber to excite and power the plasma created from the gases in the chamber.
Techniques have been developed to design and tune plasma reactors to produce acceptably uniform film thickness profiles on wafers up to about 300 millimeters in diameter. However, there is a trend toward ever increasing wafer diameters. Existing reactor designs are unable to achieve acceptable film thickness uniformity for wafers as large as 450 millimeters in diameter.